Thermal tympanic thermometer tip

ABSTRACT

A method for reducing temperature measurement error in a tympanic thermometer. The present disclosure provides a tympanic thermometer including a heat sensing probe defining a longitudinal axis and an outer surface extending from a distal end of the tympanic thermometer. The heat sensing probe includes a thermally insulating sensor housing extending to a distal end thereof. Can-packaged temperature sensing electronics are mounted at the distal portion of the sensor housing. A thermally conductive nozzle is configured to direct heat flux to the temperature sensing electronics in the distal end of the heat sensing probe. The sensor can preferably include a lip extending radially therefrom and contacting the nozzle at at least one contact point to provide heat flux to the sensor can.

CROSS REFERENCE TO RELATED APPLCIATION

The present application is a divisional of patent application Ser. No.10/480,428, filed on Dec. 10, 2003, which is a 371 of PCT/US03/11606,filed on Apr. 15, 2003, which claims benefit of U.S. Provisional PatentApplication No. 60/432,904, filed on Dec. 12, 2002, which are herebyincorporated by reference.

BACKGROUND

1. Technical Field

The present disclosure generally relates to the field of biomedicalthermometers, and more particularly, to a tympanic thermometer thatincludes a sensor having a nozzle disposed therewith that improvesaccuracy of temperature measurement.

2. Description of the Related Art

Medical thermometers are typically employed to facilitate theprevention, diagnosis and treatment of diseases, body ailments, etc. forhumans and other animals, as is known. Doctors, nurses, parents, careproviders, etc. utilize thermometers to measure a subject's bodytemperature for detecting a fever, monitoring the subject's bodytemperature, etc. An accurate reading of a subject's body temperature isrequired for effective use and should be taken from the internal or coretemperature of a subject's body. Several thermometer devices are knownfor measuring a subject's body temperature, such as, for example, glass,electronic, ear (tympanic).

Glass thermometers, however, are very slow in making measurements,typically requiring several minutes to determine body temperature. Thiscan result in discomfort to the subject, and may be very troublesomewhen taking the temperature of a small child or an invalid. Further,glass thermometers are susceptible to error and are typically accurateonly to within a degree.

Electronic thermometers minimize measurement time and improve accuracyover glass thermometers. Electronic thermometers, however, still requireapproximately thirty (30) seconds before an accurate reading can betaken and may cause discomfort in placement as the device must beinserted into the subject's mouth, rectum or axilla.

Tympanic thermometers are generally considered by the medical communityto be superior for taking a subject's temperature. Tympanic thermometersprovide rapid and accurate readings of core temperature, overcoming thedisadvantages associated with other types of thermometers. Tympanicthermometers measure temperature by sensing infrared emissions from thetympanic membrane (eardrum) in the external ear canal. The temperatureof the tympanic membrane accurately represents the body's coretemperature. Further, measuring temperature in this manner only requiresa few seconds.

Known tympanic thermometers typically include a probe containing a heatsensor such as a thermopile, a pyroelectric heat sensor, etc. Duringuse, the heat sensor is generally located outside the eardrum andutilizes a waveguide of radiant heat to transfer heat energy from theeardrum to the sensor. See, for example, U.S. Pat. Nos. 6,179,785,6,186,959, and 5,820,264. These types of heat sensors are particularlysensitive to the eardrum's radiant heat energy.

In operation, a tympanic thermometer is prepared for use and a probecover is mounted onto a sensing probe extending from a distal portion ofthe thermometer. The probe covers are hygienic to provide a sanitarybarrier and are disposable after use. A practitioner or other careprovider inserts a portion of the probe having the probe cover mountedthereon within a subject's outer ear canal to sense the infraredemissions from the tympanic membrane. The infrared light emitted fromthe tympanic membrane passes through a window of the probe cover and isdirected to the sensing probe by a waveguide. The window is typically atransparent portion of the probe cover and has a wavelength in the farinfrared range. The probe cover should provide for the easy andcomfortable insertion of the probe into the ear canal.

The practitioner presses a button or similar device to cause thethermometer to take a temperature measurement. The microelectronicsprocess electrical signals provided by the heat sensor to determineeardrum temperature and render a temperature measurement in a fewseconds or less. The probe is removed from the ear canal and the probecover is removed and discarded.

Many tympanic thermometers measure radiation being emitted from anobject, such as the tympanic membrane, by employing a thermopile sensor.A membrane inside the thermopile sensor absorbs incoming radiation,which raises the temperature of the membrane. The hot junctions ofthermocouples, which may be very small, are placed onto the membranewhile the cold junction is thermally connected to a sensor body of thethermopile sensor. The thermocouples output a voltage change that isproportional to the temperature change between the hot and coldjunctions of the thermocouple. This voltage change can be correlated tothe Stefan-Boltzmann law for emitted radiation from a black body(represented in formulaic, Vout=K(eT⁴obj−T⁴sens).

Errors in temperature readings taken by known tympanic thermometersoften occur because the temperature of the sensor body is changing dueto changing ambient temperature situations. These changing ambienttemperature situations include other factors that affect the temperatureof the thermopile sensor. For example, when a tympanic thermometer atroom temperature is placed in the human ear, heat transfers to thethermopile sensor and other portions of the tympanic thermometer. Thethermopile sensor includes sensor optics and a sensor can. The sensoroptics and can temperature are caused to increase very rapidly and thusemit radiation back to the membrane inside the thermopile sensor. Sincethe temperature of the sensor is measured back at the proximal end ofthe thermopile sensor, Tsens will not reflect the actual temperature ofthe thermopile sensor and therefore an error will be introduced to thetemperature measurement.

Transferring some known tympanic thermometers from a room temperaturesetting to a different temperature setting in the human ear is achanging ambient environment. In these types of changing ambientenvironments, data from thermal analysis and lab testing has showntemperature changes across the thermopile sensor can range as high as1.5–2.5 degrees Celsius using known nozzle configurations that aredisposed with the sensors of these tympanic thermometers. Devices ofthis kind may disadvantageously take inaccurate temperature readingsresulting in drawbacks for treating and diagnosing patients.

Therefore, it would be desirable to overcome the disadvantages anddrawbacks of the prior art with a tympanic thermometer that includes asensor having a nozzle disposed therewith that improves accuracy oftemperature measurement. It is contemplated that the tympanicthermometer and its constituent parts are easily and efficientlymanufactured and assembled.

SUMMARY

Accordingly, a tympanic thermometer is provided that includes a sensorhaving a nozzle disposed therewith that improves accuracy of temperaturemeasurement to overcome the disadvantages and drawbacks of the priorart. The tympanic thermometer is easily and efficiently manufactured andassembled. The present disclosure resolves related disadvantages anddrawbacks experienced in the art.

The present disclosure relates to a nozzle design that minimizestemperature reading errors and inaccuracy experienced in the prior artdue to changing ambient environment temperatures. Thus, a tympanicthermometer is provided, in accordance with the principles of thepresent disclosure, having a nozzle configuration that directs heat fluxto a proximal end of a sensor. Directing the thermally conducted heat tothe proximal end of the sensor allows a sensed temperature (Tsens) torise quickly with the sensor housing temperature rise due to ambientenvironment change. This configuration advantageously minimizes theassociated changes in temperature (ΔT) across the sensor can and theassociated errors involved.

The present disclosure of the nozzle design minimizes temperaturereading error in all ambient changing environments and facilitates amore stable design in its application. The nozzle configurationdisclosed provides a geometry whereby the temperature changes (ΔT)decrease to 0.2–0.4 degrees Celsius. This results provide forsignificant reductions in error.

The present disclosure provides a tympanic thermometer including a heatsensing probe defining a longitudinal axis and an outer surfaceextending from a distal end of the tympanic thermometer. The heatsensing probe includes a sensor housing extending to a distal endthereof. A sensor can is mounted with the sensor housing and a nozzle ismounted onto the sensor housing. The sensor can includes temperaturesensing electronics for sensing temperature via the heat sensing probe.The nozzle includes a base disposed with the sensor housing and anelongated cylindrical nose portion disposed about the sensor housing.The nozzle is configured to direct heat flux to the distal end of theheat sensing probe. A probe cover is mountable to the distal end of thetympanic thermometer. The probe cover has an inner surface configured toengage an outer surface of the nozzle. The sensor can preferably includea lip extending radially therefrom and contacting the nozzle at at leastone contact point to provide heat flux to the sensor can.

In an alternate embodiment, the tympanic thermometer includes athermometer body and a heat sensing probe extending from the thermometerbody. The heat sensing probe includes an elongated thermally conductivenozzle having an inner surface defining a cavity and an elongatedthermally insulating sensor housing disposed within the cavity. An airgap separates the sensor housing from the inner surface. A sensor can ismounted to a distal end of the sensor housing and contacts the innersurface of the nozzle.

The heat sensing probe preferably includes a base engaging the sensorhousing and the nozzle to provide coaxial alignment therebetween. Thebase also preferably includes structure that attaches the sensing probeto the thermometer body such as snap features, sleeve features,provisions for ultrasonic welding or provisions for fasteners such asscrews, rivets or the like.

The sensor can preferably includes at least one protrusion extendingradially outward to provide a contact point between the inner surface ofthe nozzle and the can to thereby facilitate heat flow from the can tothe nozzle. In another embodiment, the protrusion(s) can be electricallypreheated to reduce the temperature gradient in the heat sensing probe.

The sensor can preferably incorporates an infrared transmissive window,a sensor base having a distal surface and an infrared sensor disposed onthe distal surface. The infrared sensor is configured to receiveinfrared radiation through the infrared transmissive window. In anotherembodiment, the infrared sensor includes a thermistor. The disclosureprovided allows the temperature differential between the can surface andthe thermistor to remain substantially constant while ambienttemperature changes over time. The constant temperature differential isprovided by optimizing a heat conduction path between the ambientenvironment and the can surface.

A disposable probe cover is preferably disposed over the heat sensingprobe wherein the probe cover includes an infrared transmissive filmsubstantially enclosing a distal end of the probe cover and aligned witha distal opening of the nozzle.

The present disclosure provides a method for reducing temperaturemeasurement error in a tympanic thermometer by providing a thermallyconductive path between the external environment and a sensor canincorporating temperature sensing electronics in a heat sensing probe ofthe tympanic thermometer. The thermally conductive path may include anelongated thermally conductive nozzle contacting the sensor can. Thesensor can may be preheated to a predetermined temperature to reducetemperature gradients across the heat sensing probe.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the present disclosure, which are believedto be novel, are set forth with particularity in the appended claims.The present disclosure, both as to its organization and manner ofoperation, together with further objectives and advantages, may be bestunderstood by reference to the following description, taken inconnection with the accompanying drawings wherein:

FIG. 1 is a perspective view of a tympanic thermometer, in accordancewith the principles of the present disclosure, mounted with a holder;

FIG. 2 is a perspective view of the tympanic thermometer shown in FIG.1;

FIG. 3 is a perspective view of a probe cover intended for mounting tothe tympanic thermometer shown in FIG. 2;

FIG. 4 is an exploded view, with parts separated, of a distal end of thetympanic thermometer shown in FIG. 2;

FIG. 4A is a partial cross-sectional view of the probe cover mounted onthe distal end of the tympanic thermometer shown in FIG. 2;

FIG. 5 is an enlarged perspective cutaway view of the distal end of thetympanic thermometer shown in FIG. 2;

FIG. 6 is a temperature gradient plot for one embodiment of the tympanicthermometer, in accordance with the present disclosure measured at 1.072seconds after heat has been applied;

FIG. 7 is a temperature gradient plot for the embodiment of the tympanicthermometer shown in FIG. 6 measured at 3.945 seconds after heat hasbeen applied;

FIG. 8 is a temperature gradient plot for the embodiment of the tympanicthermometer shown in FIG. 6 measured at 7.229 seconds after heat hasbeen applied;

FIG. 9 is a temperature gradient plot for the embodiment of the tympanicthermometer shown in FIG. 6 measured at 10 seconds after heat has beenapplied;

FIG. 10 is a time versus temp graph of locations of the sensortemperatures for the embodiment of the tympanic thermometer for the timeperiods shown in FIG. 6–9;

FIG. 11 is a temperature gradient plot for heat flux for the embodimentof the tympanic thermometer shown in FIG. 6 measured at 1.072 secondsafter heat has been applied; and

FIG. 12 is a temperature gradient plot for heat flux for the embodimentof the tympanic thermometer shown in FIG. 6 measured at 10 seconds afterheat has been applied.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The exemplary embodiments of the tympanic thermometer and methods of usedisclosed are discussed in terms of medical thermometers for measuringbody temperature, and more particularly, in terms of a tympanicthermometer that includes a sensor having a nozzle disposed therewiththat improves accuracy of temperature measurement. It is envisioned thatthe present disclosure finds application for the prevention, diagnosisand treatment of diseases, body ailments, etc. of a subject. It isfurther envisioned that the principles relating to the tympanicthermometer disclosed include proper removal of a used probe cover viathe ejection apparatus and indication to a practitioner whether a new,unused probe is mounted to the tympanic thermometer.

In the discussion that follows, the term “proximal” will refer to theportion of a structure that is closer to a practitioner, while the term“distal” will refer to the portion that is further from thepractitioner. As used herein, the term “subject” refers to a humanpatient or other animal having its body temperature measured. Accordingto the present disclosure, the term “practitioner” refers to a doctor,nurse, parent or other care provider utilizing a tympanic thermometer tomeasure a subject's body temperature, and may include support personnel.

Reference will now be made in detail to the exemplary embodiments of thepresent disclosure, which are illustrated in the accompanying figures.Turning now to the figures wherein like components are designated bylike reference numerals throughout the several views and initially toFIGS. 1, 2 and the attached disclosure, plots, graphs and figures, thereis illustrated a tympanic thermometer 20, in accordance with theprinciples of the present disclosure.

Tympanic thermometer 20 includes a cylindrical heat sensing probe 22.Heat sensing probe 22 extends from a distal end 24 of tympanicthermometer 20 and defines a longitudinal axis x. Heat sensing probe 22may have various geometric cross-sectional configurations, such as, forexample, rectangular, elliptical, etc. A probe cover 32 is mounted todistal end 24. Probe cover 32 may be shaped, for example,frustoconically, or shaped in a tapered manner as to allow for easierinsertion into the ear of the subject and attachment and detachment fromthe heat sensing probe 22. Heat sensing probe 22 is configured to detectinfrared energy emitted by the tympanic membrane of the subject.

It is contemplated that tympanic thermometer 20 includes the necessaryelectronics and/or processing components to perform temperaturemeasurement via the tympanic membrane, as is known to one skilled in theart. It is further envisioned that tympanic thermometer 20 may include awaveguide to facilitate sensing of the tympanic membrane heat energy.Tympanic thermometer 20 is releasably mounted in a holder 40 for storagein contemplation for use. Tympanic thermometer 20 and holder 40 may befabricated from semi-rigid, rigid plastic and/or metal materialssuitable for temperature measurement and related use. It is envisionedthat holder 40 may include the electronics necessary to facilitatepowering of tympanic thermometer 20, including, for example, batterycharging capability, etc.

Referring to FIG. 3, probe cover 32 has a distal end 54 that issubstantially enclosed by a film 56. Film 56 is substantiallytransparent to infrared radiation and configured to facilitate sensingof infrared emissions by heat sensing probe 22. Film 56 isadvantageously impervious to ear wax, moisture and bacteria to preventdisease propagation.

The component portions of the probe cover, which is disposable, arefabricated from materials suitable for measuring body temperature viathe tympanic membrane with a tympanic thermometer measuring apparatus.These materials may include, for example, plastic materials, such as,for example, polypropylene, polyethylene, etc., depending on theparticular temperature measurement application and/or preference of apractitioner. The probe cover has a window portion or film that can befabricated from a material substantially transparent to infraredradiation and impervious to moisture, ear wax, bacteria, etc. The filmhas a thickness in the range of 0.0005 to 0.001 inches, although otherranges are contemplated. The film may be semi-rigid or flexible, and canbe monolithically formed with the remaining portion of the probe coveror integrally connected thereto via, for example, thermal welding, etc.One skilled in the art, however, will realize that other materials andfabrication methods suitable for assembly and manufacture, in accordancewith the present disclosure, also would be appropriate.

Referring to FIGS. 4, 4A and 5, heat sensing probe 22 includes a nozzle100, a can 102 attached to temperature sensing electronics, a sensorhousing 104 and a base 106. By way of non-limiting example, nozzle 100may be fabricated from metal or other material which aides in the rapidexchange or transfer of heat. Similarly, by way of non-limiting example,sensor housing 104 is preferably fabricated from materials which providefor less thermo transmission (i.e., more insulated) than nozzle 100, forexample, plastic or other similar matter. FIG. 4A discloses a partialcross section of the probe cover 32 as mounted onto nozzle 100 and anair gap 118 disposed therebetween. As shown, nozzle 100, sensor housing104 and can 102 are fitted in a secure relationship. Such securerelationship may be established by way of adhesive, friction, pressfitting and the like. An air gap 118 is disposed between the nozzle 100and sensor housing 104. Can 102 further includes sensor base 126,infrared sensor 122, infrared filter or window 120 and thermistor 124.

The component parts of heat sensing probe 22 are assembled and nozzle100 is mounted thereon to direct heat flux through a distally positionedsensor window at distal end 108 of heat sensing probe 22. Nozzle 100includes a base 110 and an elongated nose portion 112 that facilitatetransfer of the heat flux to distal end 108.

In operation, heat from, for example, the ear of the subject, istransferred from probe cover 32 to nozzle 100. It is contemplated hereinthat nozzle 100 may be both in physical contact with the lip 114 or in aclose proximate relationship with lip 114 of can 102. Such contactenables heat transfer from nozzle 100 to lip 114 of can 102. As shown inFIGS. 6–9 and 11–12, heat transfer to can 102 from lip 114 can occur atany local or single point of contact (FIGS. 6–9 and 11–12 disclose suchpoint of contact along an upper portion of lip 114) or along a pluralityof contact points, for example, the entire portion of lip 114.

It is contemplated herein, that can 102 may have a plurality of lips,ribs or other similar structures, for example, detents, nubs, etc.,which aide in the heat transfer from nozzle 100 to can 102 andultimately to can tip 116. Lip members 114 may also be formed in avariety of geometric configurations, e.g., helical, dashed, etc. Forexample, in order to reduce the temperature gradient from the lip 114 totip 116, (as well as the reduction of the temperature gradient frominternal thermistor 124 (FIG. 4A) and top of can 102), can 102 may havea plurality of lip members made from a metal alloy or other material.Such lip members may be made from separate materials, may be partiallyin contact with the body of can 102, or otherwise be adapted to reducethe temperature gradient from lip area 114 to can tip 116.

It is also contemplated herein, that can 102 by way of or in addition tothe lips 114 can be pre-heated electrically or by other means to certainpreset temperatures. Lip members 114 assist in heat transfer from nozzle100, such that the heat gradient from lip 114 to can tip 116 is reduced.This reduction in the gradient across the sensor tip of can 102 providesfor faster, more accurate results.

As noted above, and as opposed to other prior art temperature sensingtips, which are designed to insulate sensing tips, the tympanicthermometer of the present disclosure heats the sensor tip (can 102) byway of heat transfer from lip 114 (which receives heat from nozzle 100)in order to reduce the temperature gradient across tip 116.

As discussed and shown in the FIGS. 4, 4A and 5 above, sensor can 102 isdistally situated along the sensor housing 104 and nozzle 100. Suchrelationship provides for the sensor to be included within orsubstantially close to the ear of a subject during a temperaturereading. The prior art disclose sensor to ear relationships of thiskind; however, these prior art relationships include unique differentialheating issues of the sensor. As discussed below and shown in FIGS.6–12, the differential heating problems of the prior art have beenovercome.

By way of a non-limiting example and referring to FIGS. 6–12, oneembodiment of tympanic thermometer 20 includes heat sensing probe 22 atan initial temperature of 20° C. when a 40° C. temperature load isapplied to the outside surface of probe cover 32. This is similar totaking heat sensing probe 22 from room temperature and disposing itwithin the ear of a human subject with a fever. As shown, radiationeffects are applied to the top face of sensor housing 104 and nozzle100. A transient analysis was run for ten (10) seconds for an aluminumnozzle design with a sensor contact.

FIGS. 6–12 show temperature plots from a simulated temperature readingof the human ear. The data of such were confirmed from actualexperimental tests performed on the ear of a subject. FIG. 6 shows atemperature plot of the temperature distribution across the sensorsection of can 102 after 1.072 seconds. Areas of focus include thesurface where the absorber chip and thermistor 124 (FIG. 4A) arelocated, the inside top of the sensor can and the inside side of thesensor can. FIG. 7 shows a temperature plot of the temperaturedistribution across the sensor section after 3.945 seconds. FIG. 8 showsa temperature plot of the temperature distribution across the sensorsection after 7.229 seconds. FIG. 9 shows a temperature plot of thetemperature distribution across the sensor section after 10 seconds.FIG. 10 shows a plotted graph of the temperature distribution for the 10second time transient. As shown from the results of a nodal analysisperformed at the top, side internal thermistor 124 (FIG. 4A) of can 102,(ΔT) is substantially constant across the 10 second time transient (thatis, (ΔT) essentially tracks the thermistor 124 (FIG. 4A)). As such,temperature accuracy errors do not increase with time as in conventionalprior art thermometers. Temperature readings can occur at substantiallyany time along the plotted graph of FIG. 10. FIG. 11 shows a temperatureplot of the temperature gradient plot for heat flux after 1.072 seconds.FIG. 12 shows a temperature plot of the temperature gradient plot forheat flux after 10 seconds.

It will be understood that various modifications may be made to theembodiments disclosed herein. Therefore, the above description shouldnot be construed as limiting, but merely as exemplification of thevarious embodiments. Those skilled in the art will envision othermodifications within the scope and spirit of the claims appended hereto.

1. A method of assembling a tympanic thermometer comprising: providing aheat sensing probe including a thermally insulating sensor housing;forming the sensor housing from a thermally insulating material;mounting a sensor can on the thermally insulating sensor housing, thesensor can including temperature sensing electronics for sensingtemperature via the heat sensing probe; mounting a thermally conductivenozzle onto the thermally insulating sensor housing, said nozzleincluding a thermal conductive base and an elongated cylindrical noseportion; and configuring the nozzle, sensor can and housing to directheat flux from the distal end of the sensor can to a proximal end ofsaid sensor can and to reduce the temperature gradient from a can tip toa sensor base.
 2. The method according to claim 1 further comprisingcontacting said thermally conductive nozzle at least one contact pointwith a lip extending radially from the sensor can to provide heat fluxto said sensor can.